The gdiff-th package

Generate gdiff GADTs and Instances. Alpha, but suprisingly functional.
Very useful for unit testing large data structures. I have tested it on a
few very large collections of types and it appears to work. Although,
when I tried to compare two versions of a hackage package with src-exts
the (GDiff) performance is terrible. In my personal experience of using
gdiff in unit testing, the performance has be great. Your mileage may vary.

I wouldn't use it for sending patches over the wire or anything like that,
I am not convinced there are no bugs in my code yet. There are examples in the examples directory of the
cabal tarball. Also the main module includes an example in the documentation.